Knock and announce

Knock-and-announce, in United States law criminal procedure, is an ancient common law principle, incorporated into the Fourth Amendment, which requires law enforcement officers to announce their presence and provide residents with an opportunity to open the door prior to a search.

The rule is currently codified in the United States Code, which governs Fourth Amendment searches conducted by the federal government. Most states have similarly codified the rule into their own statutes, and remain free to interpret or augment the rule and its consequences in any fashion that remains consistent with Fourth Amendment principles. A state's knock-and-announce rule will govern searches by state actors pursuant to state-issued warrants, assuming that Federal actors are not extensively involved in the search.

English common law has required law enforcement to knock-and-announce since at least Semayne's case (1604). In Miller v. United States (1958), the Supreme Court of the United States recognized that police must give notice before making a forced entry and in Ker v. California (1963) a divided Court found that this limitation had been extended against the states by the United States Constitution.

However, in Wilson v. Arkansas (1995) the U.S. Supreme Court ruled that a knock-and-announce before entry was a factor that must be considered in reviewing the overall constitutionality of a Fourth Amendment search. After several state attempts to exclude specific categories (e.g. drug crimes) from the knock-and-announce rule, the Supreme Court in Richards v. Wisconsin prohibited the policy, and demanded a return to a case-by-case review scenario. The Richards Court suggested that the knock and announce rule could be dispensed with only in certain circumstances, for example where police have reasonable suspicion that an exigent circumstance exists. The Court read its earlier Wilson opinion to suggest that such circumstances might include those:

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